JP2014120780A - Antenna device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an antenna device capable of contributing to a miniaturized device body while suppressing the deterioration of antenna radiation efficiency.SOLUTION: The antenna device includes: a feed point 4; a first antenna element 1 composed of a conductor having one end connected to the feed point 4 and corresponding to a first frequency band; and a second antenna element 2 composed of a conductor having one end connected to the feed point 4 and corresponding to a second frequency band higher in frequency than the first frequency band. The first antenna element 1 is disposed on the second antenna element 2 side in a bent manner so that a first antenna open end portion 1a, which is an open end of the first antenna element 1, faces a second antenna open end portion 2a, which is an open end of the second antenna element 2.

Description

  The present invention relates to an antenna device for data communication, and more particularly, to a multiband antenna device.

  In recent years, in wireless communication networks, LTE (Long Term Evolution) systems are being put into practical use all over the world for the purpose of improving frequency utilization efficiency and data rate. In such an LTE system, it is determined to transmit and receive data using a plurality of different frequency bands.

  By the way, in the LTE system, it is considered to adopt a standard standard all over the world, but the frequency band that can be used in the LTE system is different for each country. FIG. 5 shows an example of frequency band allocation in each country. In FIG. 5, UL indicates an allocated frequency band in the uplink, and DL indicates an allocated frequency band in the downlink.

  As described above, the frequency band applied in the LTE system is not common in all countries, and each mobile phone service operator operates the system based on the frequency allocation of the home country. Therefore, when one terminal is to be used in a plurality of countries, an antenna device corresponding to a frequency band applied in each country, that is, a multiband has been required.

  In response to such a demand, a multiband antenna device such as the antenna device according to Patent Document 1 has been proposed.

  Here, the antenna device according to Patent Document 1 will be described with reference to FIG.

  In the antenna device 950, the first element 911 and the second element 912 are fixed to the base 901 made of insulating resin, and the short-circuit element is located close to the signal line 935 of the insulating substrate 930 made of FPC (Flexible Printed Circuit). 955. Then, in a state where the antenna device 950 is mounted on a mobile phone (not shown), by dropping the short-circuit element 955 to the ground, the unnecessary resonance of the signal line 935 is canceled by the action of the short-circuit element 955, The decline in radiation efficiency is said to be suppressed.

JP 2010-166469 A

  Thus, in the conventional antenna device 950, by providing the short-circuit element 955, it is possible to suppress a decrease in radiation efficiency. However, since the second element 912 and the short-circuit element 955 for the low frequency band are extended in the longitudinal direction of the base 901, the length of the base 901 in the longitudinal direction has to be increased. For this reason, the antenna device 950 is prevented from being downsized.

  The present invention has been made in view of the actual situation of the prior art, and an object of the present invention is to provide an antenna device that can suppress a decrease in radiation efficiency and contribute to downsizing of a main body.

  In order to solve this problem, an antenna device according to the present invention includes a first antenna element corresponding to a first frequency band, which includes a feeding point and a conductor and one end connected to the feeding point, and a conductor. An antenna apparatus comprising: a second antenna element having one end connected to the feeding point and corresponding to a second frequency band having a frequency higher than the first frequency band, the open end of the first antenna element The first antenna element is curved toward the second antenna element so that the first antenna open end and the second antenna open end that is the open end of the second antenna element face each other. It has the feature of being.

  In the antenna device configured as described above, the first antenna open end having the highest electric field strength in the first antenna element is opposed to the second antenna open end having the highest electric field strength in the second antenna element. Therefore, the capacitance component between the first antenna open end and the second antenna open end is adjusted, the separation distance between the first antenna open end and the second antenna open end, and the length of the facing conductor are adjusted. By doing so, it can be easily varied. Therefore, each impedance can be easily changed, and impedance matching between the first antenna element and the second antenna element can be performed more efficiently. Therefore, it is possible to suppress a decrease in radiation efficiency. In addition, since the first antenna element is curved toward the second antenna element, it is not necessary to increase the shape of the antenna device, which can contribute to downsizing of the antenna device body.

  In the above configuration, a ground point and a third antenna element which is made of a conductor and is not connected to the feeding point and has one end connected to the ground point, the conductor of the third antenna element Is provided along the conductor of the first antenna element.

  In the antenna device configured as described above, since the third antenna element that is not connected to the feeding point is provided along the first antenna element, the first antenna open end and the second antenna open end are separated from each other. By adjusting the distance, the third antenna element can be easily capacitively coupled to the first antenna element. Therefore, resonance by the third antenna element can be newly generated at a frequency near the resonance frequency by the first antenna element, and the bandwidth of the first frequency band can be expanded.

  In the above configuration, a conductor on the feeding point side of the first antenna element is provided along a conductor of the second antenna element, and the first antenna element, the second antenna element, and the The third antenna element is characterized in that the second antenna element, the first antenna element, and the third antenna element are arranged in parallel in this order.

  In the antenna device configured in this way, the first antenna element and the second antenna element share a feeding point, but their resonance frequencies are greatly different, so that the respective antenna currents flow into each other. It is hard to be influenced by each other. Therefore, there is no particular problem even if the first antenna element is provided along a part of the second antenna element. In addition, since the first antenna element is provided along a part of the second antenna element, each impedance matching is easily obtained. In addition, the first antenna element and the third antenna element are close in resonance frequency, but the third antenna element is physically separated from the first antenna element on the feeding side. Antenna current does not flow into the third antenna element. Therefore, it becomes difficult to be influenced by each other. Therefore, it is most preferable to arrange the second antenna element, the first antenna element, and the third antenna element in parallel in this order.

  In the above configuration, the conductor of the second antenna element is formed so that the width thereof gradually increases from one end of the second antenna element toward the open end of the second antenna. Have.

  In the antenna device configured as described above, the second antenna open end side (antenna capacity region) having the highest electric field strength among the conductors of the second antenna element is formed wide so that the antenna capacitance component increases. Will be. In general, in a resonance circuit, the resonance frequency decreases as the capacitance component increases. Therefore, the antenna device of the present invention has a length of the radiation conductor when compared with a conductor whose open end of the second antenna is not wide. Are equal, the resonance frequency is reduced. That is, by providing a wide portion at the open end of the second antenna, the length of the radiation conductor required to resonate at a desired frequency can be set short, so that the overall size of the antenna device can be easily reduced. Can be Further, since the width is gradually increased toward the second antenna open end 2a, the capacitance component of the second antenna element 2 can be gradually increased. Therefore, the reception frequency band can be set more easily.

  In the above configuration, the conductor of the third antenna element has a band-like narrow portion on the grounding point side, and a wide portion at the third antenna open end which is the open end of the third antenna element. It has the characteristic of being formed to have.

  In the antenna device configured as described above, the conductor of the third antenna element is formed to have a band-like narrow portion on the ground point side and a wide portion on the third antenna open end, The longitudinal dimension of the third antenna element can be shortened by increasing the capacitance component at the third antenna open end (antenna capacity region) and increasing the inductance component at the grounding point side (antenna induction region). This is advantageous for downsizing.

  In the antenna device of the present invention, the first antenna open end having the highest electric field strength in the first antenna element is opposed to the second antenna open end having the highest electric field strength in the second antenna element. Therefore, the capacitance component between the first antenna open end and the second antenna open end is adjusted by the distance between the first antenna open end and the second antenna open end and the length of the opposing conductor. Therefore, it can be changed more easily. As a result, the respective impedances can be easily varied, and the impedance matching between the first antenna element and the second antenna element can be performed more efficiently. Therefore, it is possible to efficiently suppress a decrease in radiation efficiency. In addition, since the first antenna element is curved toward the second antenna element, it is not necessary to increase the shape of the antenna device, which can contribute to downsizing of the antenna device.

It is a top view of the antenna apparatus which concerns on embodiment of this invention. It is a figure which shows the relationship of each frequency band of a 1st frequency band, a 2nd frequency band, and a 3rd frequency band. It is a graph which shows the frequency characteristic of VSWR (voltage standing wave ratio) of the antenna device which concerns on embodiment. It is a graph which shows the frequency characteristic of the radiation efficiency of the antenna device which concerns on embodiment. It is a figure which shows the example of a frequency band allocation of each country of a LTE system. It is a top view of the antenna device which concerns on a prior art example.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a plan view of an antenna device 100 according to the embodiment, and FIG. 2 is a diagram illustrating a relationship between frequency bands of a first frequency band, a second frequency band, and a third frequency band. FIG. 3 is a graph illustrating frequency characteristics of VSWR (voltage standing wave ratio) of the antenna device 100 according to the embodiment. FIG. 4 is a graph showing frequency characteristics of radiation efficiency of the antenna device 100 according to the embodiment.

[Embodiment]
As shown in FIG. 1, the antenna device 100 according to the embodiment includes a first antenna element 1 that includes a feeding point 4 and a grounding point 5 and includes a conductor and one end connected to the feeding point 4 and a conductor. And a second antenna element 2 having one end connected to the feeding point 4. Moreover, the third antenna element 3 is also provided which is made of a conductor and is not connected to the feeding point and has one end connected to the ground point 5. In addition, the 1st antenna element 1, the 2nd antenna element 2, and the 3rd antenna element 3 are each comprised planarly on the same plane.

  In FIG. 1, the 1st antenna element 1, the 2nd antenna element 2, and the 3rd antenna element 3 consist of metal conductors. The metal conductor may be formed by a metal foil pattern on an insulating substrate (not shown), or may have a configuration in which a metal plate is cut out and combined without using an insulating substrate.

  The antenna length of the first antenna element 1 is set to a length corresponding to the first frequency band. Specifically, the antenna length is set to about ¼ of the wavelength of the substantially central frequency of the first frequency band. Yes. The antenna length of the second antenna element 2 is set to a length corresponding to the second frequency band having a frequency higher than that of the first frequency band. Specifically, the antenna length is approximately the center frequency of the second frequency band. It is set to about 1/4 of the wavelength.

  The conductor on the feeding point side of the first antenna element 1 is provided along the conductor of the second antenna element 2. Generally, it is possible to perform impedance matching with each other by arranging the conductors of the antenna elements close to each other. The impedance of the antenna element includes an inductance component determined by the length and width of the conductor of the antenna element, and a capacitance component generated between the conductor of the antenna element and the ground, or between the conductors of two adjacent antenna elements. Determined by. In particular, a capacitance component generated between the conductors of two adjacent antenna elements by adjusting the distance between the conductors of two adjacent antenna elements and adjusting the distance between the conductors of the two adjacent antenna elements. Can be adjusted. As a result, the impedance of each antenna element can be adjusted.

  In the antenna device 100, the conductor of the first antenna element 1 is provided along the conductor of the second antenna element 2, the distance between the conductors is set to D1, and the length of the opposing conductor is set to L1. doing. Each impedance matching is performed by adjusting the dimensions of D1 and L1. This adjustment is performed at the design stage of the antenna device 100, and therefore the performance of the antenna device 100 is almost determined at the design stage.

  As shown in FIG. 1, the conductor of the first antenna element 1 extends from the feeding point 4 in a state where the width of the conductor is narrow, and is bent at a right angle in the X2 direction from the middle thereof. The conductor of the first antenna element 1 is further extended and bent at a right angle to the direction of the second antenna open end 2a (Y2 direction) at a distance L4. Further, the first antenna open end 1a is formed at a place where the width is further extended (L2) and further extended and the distance L5 is extended. As a result, the first antenna open end 1a, which is the open end of the first antenna element 1, and the second antenna open end 2a, which is the open end of the second antenna element 2, face each other with a separation distance D2. become. Thus, the first antenna element 1 is provided to be curved toward the second antenna element 2 side.

  In a general antenna device, the electric field strength is highest at the open end of the antenna element, and the capacitance component between the open end of the antenna element and the ground is compared with the capacitance component between the other part of the antenna element and the ground. And become the maximum. Further, when the open ends of the two antenna elements are opposed to each other like the first antenna element 1 and the second antenna element 2, the capacitance component between the open ends is between the other conductor portions. It becomes the maximum in comparison. Therefore, as described above, it is possible to perform impedance matching by bringing the conductors of the antenna elements close to each other. However, if the conductors are the open ends of the two antenna elements, it is most efficient. Impedance matching can be performed.

  In the antenna device 100 of the present embodiment, the first antenna open end 1a having the highest electric field strength in the first antenna element 1 and the second antenna open end 2a having the highest electric field strength in the second antenna element 2 are opposed to each other. I did it. Therefore, the capacitance component between the first antenna open end 1a and the second antenna open end 2a is opposed to the separation distance D2 between the first antenna open end 1a and the second antenna open end 2a. By adjusting the length L2 of the conductor, it can be easily varied. Therefore, each impedance can be easily changed, and each impedance matching of the first antenna element 1 and the second antenna element 2 can be performed more efficiently. As a result, a decrease in radiation efficiency can be further suppressed. In addition, since the first antenna element 1 is curved toward the second antenna element 2, it is not necessary to increase the shape of the antenna device 100, which can contribute to downsizing of the antenna device 100.

  As shown in FIG. 1, the first antenna element 1 is curved toward the second antenna element 2 to provide a conductor of the first antenna element 1 and the second antenna open end of the second antenna element 2. A rectangular space 6 is formed with the conductor 2a. The impedances of the first antenna element 1 and the second antenna element 2 can also be adjusted by adjusting the sizes L4 and L5 of each side of the rectangular space 6.

  As can be seen from FIG. 1, the conductor of the third antenna element 3 is provided along the conductor on the feeding point 4 side of the first antenna element 1. The third antenna element 3 is provided to widen the first frequency band of the first antenna element 1 and is a parasitic element made of a conductor that is not connected to a feeding point. By causing the conductor of the third antenna element 3 to follow the conductor of the first antenna element 1 that is a feeding element with a distance D3 that is very short compared to the wavelength of the resonance frequency of the third antenna element 3, the third antenna The element 3 can be capacitively coupled to the first antenna element 1. That is, the third antenna element 3 is fed from the first antenna element 1 and becomes an antenna element having a new resonance frequency.

  The antenna length of the third antenna element 3 is set somewhat shorter than the antenna length of the first antenna element 1. Accordingly, the new resonance frequency by the third antenna element 3 becomes higher than the resonance frequency of the first antenna element 1, and as a result, the first frequency band can be expanded to a higher level. Therefore, the first frequency band can be widened.

  The second antenna element 2 is configured such that one end thereof is connected to the feeding point 4 and the width gradually increases from one end toward the open end. It has a substantially triangular shape with two vertices. The open end of the second antenna element 2 forms a second antenna open end 2a by a side corresponding to the base of a triangle having the feeding point 4 as a vertex. The second antenna open end 2 a is the portion with the highest electric field strength in the second antenna element 2.

  Since the second antenna open end 2a (antenna capacity region) having the highest electric field strength among the conductors of the second antenna element 2 is formed wide, the capacitance component is further increased. In general, in a resonance circuit, the resonance frequency decreases as the capacitance component increases. Therefore, when compared to a conductor whose open end is not wide, the antenna resonance frequency is small if the length of the antenna radiation conductor is the same. Become. That is, by making the antenna open end 2a wide, the length of the radiation conductor required to resonate at a desired frequency can be set shorter, so the overall size of the antenna device can be easily reduced. it can.

  Further, since the width is gradually increased toward the second antenna open end 2a, the capacitance component of the second antenna element 2 can be gradually increased. Therefore, the reception frequency band can be set more easily.

  The conductor of the third antenna element 3 has a band-like narrow portion on the grounding point 5 side, and is formed to have a wide portion on the third antenna open end 3a.

  With this configuration, the capacitance component at the third antenna open end 3a is increased. Further, since the conductor on the grounding point 5 side has a band-like narrow portion, the inductance component can be increased. Thus, since the capacitance component and the inductance component can be increased simultaneously, the impedance can be adjusted more efficiently. At the same time, the longitudinal dimension of the third antenna element 3 can be significantly shortened, and the miniaturization of the antenna device 100 can be facilitated.

  As shown in FIG. 1, the first antenna element 1, the second antenna element 2, and the third antenna element 3 are arranged in parallel in the order of the second antenna element 2, the first antenna element 1, and the third antenna element 3. ing.

  The first antenna element 1 and the second antenna element 2 share the feeding point 4, but their resonance frequencies are greatly different, so that they are not easily influenced by each other even if they are installed close to each other. ing. In addition, since the first antenna element 1 is provided along a part of the second antenna element 2, as described above, each impedance matching can be easily obtained. The conductor of the third antenna element 3 is provided close to the conductor of the first antenna element 1 in order to receive power from the first antenna element 1. The conductor of one antenna element 1 is not directly connected. Therefore, the antenna current from the first antenna element 1 does not flow directly into the third antenna element 3 and is not affected by each other. Therefore, it is most preferable to arrange the antenna elements in parallel in the order of the second antenna element 2, the first antenna element 1, and the third antenna element 3.

  FIG. 2 shows frequency bands that the antenna device 100 supports.

  The frequency band from 0.7 GHz to 0.96 GHz shown in FIG. 2, that is, the first frequency band is provided by the first antenna element 1 shown in FIG. Also, the frequency band from 1.7 GHz to 2.2 GHz, that is, the second frequency band is provided by the second antenna element 2 shown in FIG.

  By the way, the antenna length of the first antenna element 1 is set so that not only the frequency band of 0.7 GHz to 0.96 GHz, that is, the first frequency band but also other frequency bands are configured. Yes.

  The first antenna element 1 sets a predetermined frequency in the first frequency band so that the frequency band of 0.7 GHz to 0.96 GHz, that is, the first frequency band can be transmitted and received, and the antenna length of the first antenna element 1 Is set to 1/4 of the wavelength of the predetermined frequency. Here, it is preferable that the predetermined frequency in the first frequency band is set to a substantially central frequency in the first frequency band. At the same time, the antenna length of the first antenna element 1 is configured to transmit and receive a frequency band from 2.5 GHz to 2.7 GHz corresponding to a frequency band approximately three times the first frequency band, that is, the third frequency band. . Specifically, the antenna length of the first antenna element 1 is set to 3/4 of the wavelength of the predetermined frequency in the third frequency band. Here, the predetermined frequency in the third frequency band corresponds to a frequency about three times the predetermined frequency in the first frequency band.

  As described above, the antenna length of the first antenna element 1 is set so that the first frequency band can be transmitted and received, and at the same time, the third frequency band corresponding to about three times the first frequency band can be transmitted and received. Will be set as follows. Therefore, transmission / reception in two frequency bands having significantly different frequencies can be realized with only one element. Therefore, it is possible to contribute to downsizing of the multiband antenna device 100.

  FIG. 3 shows the frequency characteristics of the voltage standing wave ratio (VSWR) of the antenna apparatus 100, and FIG. 4 shows the frequency characteristics of the radiation efficiency (Radiation Efficiency) of the antenna apparatus 100. 3 and 4 show the results of setting / adjusting the first antenna element 1, the second antenna element 2, and the third antenna element 3 so that the VSWR and radiation efficiency of the antenna device 100 exhibit the best characteristics. Is shown.

  In both FIG. 3 and FIG. 4, the horizontal axis indicates the frequency. The VSWR on the vertical axis in FIG. 3 indicates the degree of impedance matching, and the closer to 1, the better the characteristics. The radiation efficiency on the vertical axis in FIG. 4 indicates that the antenna loss is small, and the closer to 0 dB, the better the characteristics.

  As shown in FIG. 3, in the first frequency band from 0.7 GHz to 0.96 GHz, the second frequency band from 1.7 GHz to 2.2 GHz, and the third frequency band from 2.5 GHz to 2.7 GHz, VSWR is Each shows good characteristics of 3 or less.

  In the graph of VSWR shown in FIG. 3, in addition to the main resonance point of the first frequency band around 800 MHz, another resonance point is seen around 1000 MHz, and the first frequency band due to the third antenna element 3 is expanded. The effect can be confirmed.

  Further, in the VSWR graph shown in FIG. 3, a resonance point is observed around 2600 MHz, and the effect of setting the antenna length of the first antenna element 1 to 3/4 of the wavelength of the predetermined frequency in the third frequency band. Can be confirmed.

  As shown in FIG. 4, in the first frequency band from 0.7 GHz to 0.96 GHz, the radiation efficiency shows a characteristic having a practically no problem level of about −1.8 dB or more. In addition, in the second frequency band from 1.7 GHz to 2.2 GHz and the third frequency band from 2.5 GHz to 2.7 GHz, the radiation efficiency exhibits very good characteristics of about −0.7 dB or more, respectively. Yes.

  By the way, the antenna device 100 which concerns on embodiment of this invention assumes the antenna device mounted in moving bodies, such as a vehicle. As shown in FIG. 1, the antenna device 100 has a feeding point 4 and a grounding point 5 in the Y2 direction, extends in the Y1 direction, and extends in the X1 direction as it extends in the Y1 direction. Yes. This shape is generally called a shark fin, and may be attached to the roof of a vehicle such as a luxury car. The antenna device 100 in this case is made of a metal plate, and when attached to the roof of the vehicle, the antenna device 100 is attached perpendicularly to the surface of the roof with the Y1 direction facing up.

  When the antenna device 100 is mounted on a vehicle or the like, it can be considered that the antenna device 100 is mounted inside the vehicle in addition to the vehicle roof. In that case, it is possible to print the antenna device 100 on a film-like substrate such as an FPC (Flexible Printed Circuit) and attach it to the inside of the windshield of the vehicle.

  The antenna device 100 of the present invention has been described on the assumption that it is used in the LTE system. However, other than the LTE system, for example, an existing data communication system such as 2G or 3G (W-CDMA, CDMA2000, etc.) is also used. Of course, it can be applied.

  Band11 (UL1427.9-1447.9 MHz, UL1475.9-1495.9 MHz) is shown in the column of Japan in the frequency band allocation example of FIG. However, the Band 11 is not included in the first to third frequency bands of the antenna device 100 according to the embodiment of the present invention as shown in FIG.

  At this time, since Band 11 is not put into practical use, it is not included in the frequency band of the antenna device 100 of the present invention, but may be put into practical use in the future. In the future, when it is put into practical use, it is sufficiently possible to configure so that this Band 11 can also be transmitted and received by applying the present invention.

  As described above, the antenna device 100 according to the embodiment of the present invention has been described. However, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention. It is.

  As described above, the antenna device 100 of the present invention includes the first antenna open end 1a that is the open end of the first antenna element 1 and the second antenna open end 2a that is the open end of the second antenna element 2. Were provided to face each other. Therefore, impedance matching between the first antenna element 1 and the second antenna element 2 is easier to perform, and a reduction in radiation efficiency can be suppressed. In addition, since the first antenna element 1 is provided so as to bend toward the second antenna element 2, it is not necessary to increase the shape of the antenna device 100, which can contribute to downsizing of the main body of the antenna device 100.

DESCRIPTION OF SYMBOLS 1 1st antenna element 1a 1st antenna open end part 2 2nd antenna element 2a 2nd antenna open end part 3 3rd antenna element 3a 3rd antenna open end part 4 Feeding point 5 Grounding point 6 Space 100 Antenna apparatus

Claims (5)

A first antenna element corresponding to the first frequency band, which is composed of a feeding point and a conductor and connected at one end to the feeding point, and a conductor and one end is connected to the feeding point, from the first frequency band An antenna device including a second antenna element corresponding to a high frequency second frequency band,
The first antenna element is the second antenna so that the first antenna open end which is the open end of the first antenna element and the second antenna open end which is the open end of the second antenna element face each other. An antenna device, wherein the antenna device is curved on the element side. A ground point and a third antenna element made of a conductor and not connected to the feeding point and having one end connected to the ground point;
The antenna device according to claim 1, wherein the conductor of the third antenna element is provided along the conductor of the first antenna element. A conductor on the feeding point side of the first antenna element is provided along a conductor of the second antenna element;
The first antenna element, the second antenna element, and the third antenna element are arranged in parallel in the order of the second antenna element, the first antenna element, and the third antenna element. The antenna device according to claim 2.   The conductor of the second antenna element is formed so that its width gradually increases from one end of the second antenna element toward the open end of the second antenna. Item 4. The antenna device according to any one of Items 3 to 4.   The conductor of the third antenna element has a band-like narrow portion on the grounding point side, and is formed to have a wide portion at the third antenna open end, which is the open end of the third antenna element. The antenna device according to any one of claims 2 to 4, wherein the antenna device is provided.